Lithocholic acid, a bile acid derived from the action of colonic bacteria on chenodeoxycholic acid, is known for its toxic effects on the liver and biliary tract. Sulfation has been shown to play a role in detoxifying this substance by enhancing its excretion from the body. Bile salt sulfotransferase, the enzyme responsible for bile salt sulfation has been identified. The purpose of this study is to isolate and characterize this enzyme from rat and guinea pig livers. Developmental studies of bile salt sulfotransferase show that this enzyme is inducible in the fetal liver by exposure to maternal lithocholic acid in utero, and that its production is also regulated by sex hormones. Work is currently in progress to characterize and elucidate the mechanisms which regulates the activity of bile salt sulfotransferase. These studies will provide important basic information for our understanding of bile salt sulfation.